Vascular prostheses composed of a tubular porous body formed of a synthetic resin such as polytetrafluoroethylene (hereinafter abbreviated as "PTFE") or polyester are widely used in repair of circulation or for internal shunts upon dialysis. However, such vascular prostheses involve a serious problem that they tend to be infected with bacteria. More specifically, the bacteria entered upon implantation of a vascular prosthesis, or the like are easy to proliferate on an artificial material such as the vascular prosthesis because an immune system, which is an innate protective system in the living body, is hard to normally and sufficiently operate in such circumstances. In addition, tissue cells and intracellular substances damaged or destroyed by grafting, or blood coagulation occurred in the damaged site provide suitable proliferative sites for the entered bacteria.
As methods for preventing the bacterial infection, for example, it has been conducted to sterilize a vascular prosthesis before its use, and to make a surgical field thoroughly sterile. However, the infection rate is considerably high as reported to be 1-5%. In order to treat an infectious disease, it is conducted to administer one or more antibiotics. By this method, however, it is difficult to topically exert their antibacterial effect on the site in which bacteria are grown. It has hence been only necessary to excise or remove the vascular prosthesis once it has become infected.
As methods for protecting a vascular prosthesis from bacterial infection, there have heretofore been proposed various methods in which an antibacterial activity is imparted to the vascular prosthesis itself. For example, there have been proposed (1) a vascular prosthesis obtained by applying or depositing a silver-antibiotic complex on a porous structure formed of PTFE or polyester [A. I. Benvenisty et al., J. Surgical Research, 44, 1-7 (1988)], and (2) a vascular prosthesis obtained by coating a PTFE or polyester material with a surfactant and then bonding an antibiotic to the surfactant by ionic bonding [W. B. Shue et al., J. Vascular Surgery, 8, 600-605 (1988)]. However, these methods have involved problems that it is impossible to last the antibacterial effect of the antibiotic over a long period of time until peripheral tissues including the interior of the wall of the vascular prosthesis become healed because the amount of the antibiotic combined is small, and that the antibiotic and surfactant present in the wall and on the inner wall surface of the vascular prosthesis impair the innate antithrombogenicity and histocompatibility in the vascular prosthesis.
In addition to the above methods, there have been proposed (3) methods in which a mixture of a biopolymer such as glucosaminoglycan-keratin or collagen and an antibiotic is applied onto the inner wall or outer surface of a vascular prosthesis [K. R. Sobinsky et al., Surgery, 100, 629-634 (1986), and M. D. Colburn et al., J. Vascular Surgery, 16, 651-660 (1992)]. According to these methods, the amount of the antibiotic to be combined can be increased, and the release rate of the antibiotic can be controlled. However, the methods have involved, in addition to a problem that the antibiotic and biopolymer present in the wall and on the inner wall surface of the vascular prosthesis impair the innate antithrombogenicity and histocompatibility in the vascular prosthesis, a problem that since the porous structure within the wall of the vascular prosthesis is filled with the biopolymer, the penetration of living tissues through the outer and inner walls is not caused to progress, and so the healing of the vascular prosthesis is not performed.